No, that’s not what I meant. Sorry I should have been more clear. I don’t know whether the behavior is right or wrong. I’m just saying that it won’t work like that on shared hosting, because by design you can’t connect to localhost and get your ownCloud instance.
I’ve had a quick search in the updater code for localhost and found that at some point it is trying to fall back to localhost because it wasn’t able to connect to anything else.
So I would recommend to double check your trusted domains and make sure they are correct and don’t include localhost in your config.php.
Regarding your hosting question, I decided to move this discussion to a different topic: